This paper presents a case study on one section of the regional road from the program of agglomeration analysing design solution, selection of the materials used for backfilling, backfilling method, and compaction of placed materials. It is compared to international standards and recommendations. Unexpected settlement and sinking occurred after completion of the work, and they were assessed to be due to the presence of water which was not detected during site investigation and possible internal erosion within the backfilled materials. The special laboratory testing was prescribed and conducted with the aim to measure sensitivity of prescribed material to erosion. In addition to the above, some trial work on the site was carried out by controlling thickness of the placed layers and compaction methods which proved to provide good results. In conclusion, the authors emphasise importance of the adequate site investigation, design details, technical specification and compaction technology to achieve suitable outcome.

agglomeration, roads, design, testing